The invention is related to light emitting devices, and in particular to light emitting devices having indirect bandgap materials.
Truly green semiconductor lasers and LEDs featuring an emission peak wavelength of 530-532 nm, have been a missing component for high quality full color display. InGaN lasers and LEDs emit a bluish-green color at 515 nm, while InGaP lasers and LEDs emit a yellowish-green color at 571 nm. For InGaN system, shifting the emission wavelength to 530 nm is mainly limited by the difficulty in growing high quality, high indium content materials. For InGaP system, tuning the wavelength to 530 nm is limited by a direct-to-indirect gap transition at a Ga content of >72%. Currently, green lasers are achieved by frequency doubling an infrared laser with nonlinear optical materials. However, the efficiency is usually limited to a few percent. much lower than typical semiconductor lasers.